A display device is configured to include a display panel having a display plane displaying an image on the front surface thereof, a backlight unit having a light source to illuminate the display panel, and the like. The display panel using an active matrix driving method includes a thin-film substrate. A plurality of source lines are formed in one direction in the thin-film substrate, and a plurality of gate lines are formed in the direction perpendicular to the one direction in the thin-film substrate. The intersection areas of the source lines and the gate lines become unit pixels of which driving is controlled by thin-film transistors. A predetermined source signal is applied from a source driving unit to each source line, and a predetermined gate signal is applied from a gate driving unit to each gate line. By driving control of the source driving unit and the gate driving unit, a desired image is displayed on the display panel (for example, refer to Japanese Patent No. 5032199).
Until recent years, a cold cathode fluorescent lamp (CCFL) had been widely used as a light source. However, the cold cathode fluorescent lamp has problems in that a reflecting plate is necessarily provided and thickness and weight of the display device are increased. In addition, there is also a problem in that energy efficiency is low.
Therefore, in order to reduce the thickness and weight of the display device, a light-emitting diode (LED: laser emitting diode) is used as a light source.